for the series of "[number] mi yodeya" questions

This tag is precisely for the "[number] mi yodeya" ("who knows [number]?") series of questions originated on this site's predecessor, mi.yodeya. It started with "Echad - mi yodeya?" ("who knows one?") and continues; as of this posting it is up to "Shemona Ushloshim Ushlosh Meyot - mi yodeya?" ("Who knows three hundred thirty eight?").

The series is patterned after a song sung at the seder.

Note that this series does not necessarily represent a good on-topic question here according to current standards but has been grandfathered in. Please take that into account before criticizing these questions or using them as precedent towards new 'series' questions.